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HomeMy WebLinkAboutSoils Report for Foundation DesignCIVCO Engineering, Inc. Civil Engineering Consultants P.O. Box 1758 365 West 50 North, Suite W-1 Vernal, Utah 84078 January 8, 2020 Richard Ruse Clayton Homes 67123 Road Grand Junction, CO 81505 Dear Richard, Subpet Soil Irry tl!un—Wgters Rice at Tract 25 dt 237, 11111111% CO I am writing to report the findings of a soil investigation that was conducted at the proposed site for the Wafters residence at Tract 25 County Road 237, Silt, Colorado'. -The investigation entailed the analysis of one soil sample that was taken at approximately the location and bearing depth of the proposed foundation. Testing of the soil sample included a sieve analysis and Atterberg Limits tasting. The results of the sort testing were used to classify the sal sample as 'CL - Sandy Lean Clad according to the Unified Soil Classification System. A copy of the soil data is included with this letter. CL soils are inorganic days of tow to medium plasticity. In addition to clay partides, CL soils may contain a fair amount of gravel-, sand-, and sift -sized particles. The sample tested contained a sizable proportion (47.8%) of particles that are sand -sized (fl200 Sieve) or larger. Literature suggests that medium to stiff CL soils are lively to have bearing capacities in the range of 4,000 psf. Recognizing that no specific bearing capacity testing was performed, I recommend that a more conservative bearing capacity of 2000 psf be used for design purposes. Over the years, a number of studies have been conducted in an effort to correlate sal expansiveness to atterberg limit data. According to one study, soils with Liquid Limits less than 50% and Plasd* Indices that less than 2504 generally have a tow potential for expansion (Snethen, Johnson, and Patrick 1977). The soil sample tested was found to have a Liquid Limit of 31% and a Plasticity Index of 11 % Thus, according to the referenced study, the soil in question is anticipated to have a tow expansion potential. It should be noted that Atterberg Limits testing does not address mineralogy and thus may have a limited abFdy to reliably predict soil expansion potential. CL soils often are susceptible to frost heave. Methods should be implemented to lessen the likelihood of frost heave. Foundations should extend to below frost depth or be fros4roteated by some other means. Water should be kept away from the foundation. Walkways, driveways, and ground surfaces should be graded to flow away from the foundation. Gutter down -spout outlets should be kept at least five feet away from the foundation. Vegetation requiring significant watering should not be planted near the foundation. No testing was done to determine the soirs collapse potential. In my experience, foundation failures due to soil collapse are generally, even more catastrophic than failures due to soil expansiom In every instance of soil collapse failure that I have investigated, the damaged home was located at the mouth of a pronounced drainage, such as a canyon or gully where the soil has been deposited afluvially by intermittent runoff water flows. Alluvially- deposited soils are typo* not very dense and derive their strength from mineral bonds that form between soil particles. When these soils become wet, the mineral bonds dissolve, allowing the soil particles to consolidate (collapse) under any load that is in excess of that which existed when the mineral bonds origirially formed. Mwm (435)789-5448 * Fax (435)789-4485 Email: vaneekirg@civeoengineering.com e Page 2 January8, 2020 Verify that the project site is not at the mouth of any obvious drainage. Implementing the aforementioned methods for lowering the risk of frost heave is also key to lessening the risk of soil collapse failure. In summary, the sal under the foundation was not specifically tested to determine its expansiveness but results of atterberg limits testing suggest that the sod has a low expansion potential. likewise, the soil was riot specifically tested to determine bearing capacity but was found to be of a type having characteristic bearing capacities in the range of 4000 psf. For design purposes, a 2000 psf bearing capacity is recommended. No specific testing was performed to determine the collapse potential of the soil. The home owner should make every effort to keep moisture from being introduced to the soil near the foundation. Any future purchaser of the home should be apprised of the underlying soil characteristics and the importance of keeping moisture away from the foundation. This concludes my report. Please note that this investigation was -performed for the purpose of providing general information regarding the soil underlying the proposed home and makes no prediction of foundational performance. This report should not be regarded as documentation of a geotechnical investigation as I am not a geotechnical engineer and this study was riot conducted to any generally accepted standard of geotechnical engineering practice. Please contact me ti you have questions regarding this report. Sincerely, d REGIs� a ok�'��n �•►,��. ate: ❑ t5 M. a Vance V. King, PE Engineer CIVCO Engineering, Inc. Enclosure Cc: Project File Q. C. Testing. Inc 2944 S 1500 E VERNAL, UTAH 84078 Phone (435) 789-0220 Fax (435) 781-1876 SIEVE ANALYSIS AND ATTEBERG LIMITS Project No. or Client Material Type: Distance from CL• CNCO Engineering - Walters ressdence. Silt. CO native - unified soil classification Stations: Depth: Date Sampled AASHTO T-27 Coarse Gradation Sieve Size Weight Ret % Ret. % Total Passing Sieve Size Specs 3" psmm4 3" 1" QSmm) 1" 3/4" (19mm) 314" i!2" (125mm) 1/2" 3V (9.5mm) 3/6" 94(4.75mm) #4 -4 (4.75nw) WET WT. Aft (4.75mm) DRY WT. Total MF-- Tested By TD 177 Or, ------, Remarks SOIL CLASSIFICATION (unified) 0. C-iv ESTING Date Tested: 12113/2019 UNIFIED Atterberg Limit IUquid Lima 31 iPlestic Lint 20 �Ptesic index 11 -Ckwsffim on I CL-sandy lean clay -94 Moisture Data Wet Wt 566.6 Dry WL 531.9 H2O WL 34.7 H2O % 6.1 Washed Dry Wt 355.9